WASHINGTON -- The United States should ban human reproductive cloning aimed at creating a child, says a new National Academies' report that considers only the scientific and medical aspects of this issue, plus ethical issues that pertain to human-subjects research. Based on experience with reproductive cloning in animals, the report concludes that human reproductive cloning would be dangerous for the woman, fetus, and newborn, and is likely to fail. The study panel did not address the issue of whether human reproductive cloning, even if it were found to be medically safe, would be -- or would not be -- acceptable to individuals or society.

"Data on the reproductive cloning of animals demonstrate that only a small percentage of attempts are successful, many of the clones die during all stages of gestation, newborn clones often are abnormal or die, and the procedures may carry serious risks for the mother," said Irving L. Weissman, chair of the panel that wrote the report and professor of pathology, cancer biology, and developmental biology, Stanford University, Stanford, Calif. "The proposed ban on human cloning should be reviewed within five years, but it should be reconsidered only if a new scientific review indicates that the procedures are likely to be safe and effective, and if a broad national dialogue on societal, religious, and ethical issues suggests that reconsideration is warranted."

Enacting a legally enforceable ban that carries substantial penalties would be the best way to discourage human reproductive cloning experiments in both the public and private sectors, the report says. A voluntary measure probably would not be effective because many of the technologies needed to accomplish human reproductive cloning are widely accessible in private fertility clinics and other organizations that are not subject to federal regulations.

What Does Cloning Entail?

Human reproductive cloning is an assisted reproductive technology that would be carried out with the goal of creating a newborn genetically identical to another human being. The method used to initiate the reproductive cloning procedure is called either nuclear transplantation or somatic cell nuclear transfer.

The initial step involves removing the nucleus of an egg cell and replacing it with the nucleus of a cell from an adult. The reconstructed egg is then stimulated to begin dividing. If the procedure is successful, the cell will divide several times to produce a pre-implantation embryo -- "blastocyst" -- that is composed of about 150 cells.

If the blastocyst is placed in a uterus, it can implant and form a fetus, which then may develop further and result in a newborn. Individuals created in this way would have the same nuclear genes as the original adult cells, but they would not be exact copies of the adults because of different prenatal and postnatal environments, as well as experiences.

There is a related but different procedure, which the panel denotes as nuclear transplantation to produce stem cells -- but which also has been called nonreproductive cloning, therapeutic cloning, research cloning, or somatic cell nuclear transfer to produce stem cells -- whose aim is the creation of embryonic stem cells for clinical and research purposes. Unlike reproductive cloning, the creation of embryonic stem cells by nuclear transplantation does not involve implantation of a blastocyst in a uterus.

Instead, cells are isolated from a blastocyst about five days after the nuclear transplantation procedure and used to make stem cell lines for further study and clinical applications. Such stem cells are unspecialized cells that can renew themselves indefinitely and, under the right conditions, develop into more mature cells with specialized functions. Stem cells derived from a cell nucleus of a patient could be powerful tools for medical research and improved therapies for treating disease.

Implications for Stem Cell Research

The panel concluded that the scientific and medical considerations that justify a ban on human reproductive cloning at this time are not applicable to nuclear transplantation to produce stem cells. Because of the considerable potential for developing new medical therapies to treat life-threatening diseases and advancing biomedical knowledge, the panel supported the conclusion of a previous National Academies' report -- Stem Cells and the Future of Regenerative Medicine-- that recommends that biomedical research using nuclear transplantation to produce stem cells be permitted.

The panel also encouraged a broad national dialogue on the societal, religious, and ethical issues concerning this matter.

Human Reproductive Cloning Would Be Risky

To date, five mammalian species -- sheep, cattle, pigs, goats, and mice -- have been used extensively in reproductive cloning studies. Data from these experiments clearly illustrate the problems involved and are quite compelling, the report says. Typically, very few cloning attempts are successful. Many clones die in utero -- even at late stages or soon after birth -- and those that survive frequently exhibit severe birth defects. In addition, female animals carrying cloned fetuses may face serious risks, including death from cloning-related complications. Human reproductive cloning is likely to have similar negative outcomes.

Because many eggs are needed for human reproductive cloning attempts, human experimentation could subject more women to adverse health effects -- either from high levels of hormones used to stimulate egg production or because more women overall would be sought to donate eggs, which involves surgery with its own inherent risks, the panel noted. Some proponents of human reproductive cloning have argued that voluntary, informed consent would give people the option of making their own decisions about participating in research. But when critical information is lacking, as it would be in this case, fully informing patients of potential health effects is difficult or impossible. Moreover, the cloned offspring -- who would face the greatest risks of abnormality and death -- would not be in a position to offer consent. These circumstances provide additional reasons to exercise caution, the report says.

Consideration of Ethical Issues

The panel stressed that all concerned segments of society should examine and debate the broad societal, religious, and ethical issues associated with human reproductive cloning, as well as those associated with nuclear transplantation to produce stem cells. Although this report focuses on the scientific and medical aspects of these areas, it should help to inform this broader consideration by society.

The panel's work was sponsored by the National Academies, which comprise the National Research Council, National Academy of Sciences, National Academy of Engineering, and Institute of Medicine. They are private, nonprofit institutions that provide science, technology, and health policy advice under a congressional charter. A panel roster follows.Read the full text of Scientific and Medical Aspects of Human Reproductive Cloningfor free on the Web, as well as more than 1,800 other publications from the National Academies. Printed copies are available for purchase from the National Academy Press Web site or by calling (202) 334-3313 or 1-800-624-6242. Reporters may obtain a copy from the Office of News and Public Information (contacts listed above).

Judith G. Hall, O.C., M.D.Clinical Geneticist and Pediatrician, andProfessor of Pediatrics and Medical GeneticsDepartment of PediatricsUniversity of British ColumbiaChildren's and Women's Health Centre of British ColumbiaVancouver, Canada

Robert B. Jaffe, M.D.2Fred Gellert Professor of Reproductive Medicine and Biology, and Director, Center for Reproductive SciencesDepartment of Obstetrics, Gynecology, and Reproductive SciencesSchool of MedicineUniversity of California San Francisco

Corey S. Goodman, Ph.D.1 ChairBoard on Life Sciences National Research Council, andPresident and Chief Executive OfficerRenovis Inc., andProfessor of NeurobiologyDepartment of Molecular and Cell BiologyUniversity of CaliforniaBerkeley